The invention relates to a switching unit which is composed of a set of switching valves and is suitable for making a first and a second medium flow through one of two plate coolers as desired.
Plate coolers are useful items of equipment for cooling hot oil which comes from machines using a flow of water. The oil and the cooling water are passed through the gaps between the plates in countercurrent to one another, with the result that the oil, in view of the large contact area of the plates, is efficiently cooled. From time to time, the plate cooler has to be cleaned, in order to prevent the machine in which the oil is used as lubricant from having to be shut down. Therefore, it is known to add two plate coolers to the machine. By means of a switching unit which is referred to in the preamble, it is possible to ensure that switching from the one plate cooler to the other plate cooler can take place without interruption to the oil cooling.
Known embodiments of the switching unit have eight two-way ball valves which are each mounted on a plate cooler and are formed into a unit by means of pipe systems. The switching from the one plate cooler to the other plate cooler takes place by firstly opening a set of four valves, then opening a second set of four valves and finally closing the first set of four valves. Switching errors may occur, with the result that the cooling of the lubricating oil of the machine, for example a ship propulsion engine, is endangered.
It is an object of the invention to avoid this drawback and to provide a switching unit which is referred to in the preamble and which precludes switching errors and takes up less space.
According to the invention, to this end the switching unit is characterized in that the switching unit has four switching valves, namely:
a first three-way switching valve allowing the first medium to be supplied to the one plate cooler or the other plate cooler,
a second three-way switching valve allowing the first medium to be discharged from the one plate cooler or the other plate cooler,
a third three-way switching valve allowing the second medium to be supplied to the one plate cooler or the other plate cooler,
a fourth switching valve allowing the second medium to be discharged from the one plate cooler or the other plate cooler, and in that the valve bodies of the four valves are connected to one another by an actuating mechanism, in such a manner that when one of the four valves is switched the other three valves are also switched.
Preferably, the valve bodies of the first and second valves are arranged on a first common rotation axle and the valve bodies of the third and fourth valves are mounted on a second common rotation axle, and the first and second rotation axles are coupled to one another by a transmission, in such a manner that, when one of the axles rotates, the supply and discharge of the first medium to and from the one plate cooler is switched to the supply and discharge of the first medium to and from the other plate cooler, and also the supply and discharge of the second medium to and from the said one plate cooler is switched to the supply and discharge of the second medium to and from the said other plate cooler.
It is possible to make do with one actuating handle on one of the common axles.
In order not to produce any pressure shocks caused by flow blockages when switching from the one plate cooler to the other plate cooler, use is made of ball valves, the two limit positions of each of the rotation angles forming an angle of 90xc2x0 with one another and a flow connection to two plate coolers being present in an intermediate position which lies at approximately 45xc2x0 from the two limit positions.